Hypothetical is good!!
My first comment is regarding the "matching" statement. If the pistol was advertised as all matching, I would expect all parts to "properly" match. That means, at least to me, the requisite metal parts and the grips (if they are suppose to be matching) and the magazine. If the magazine isn't matching, it is the sellers obligation to state that upfront, IMO.
Next, the suffix. I agree with Stu, in that unless it has an affect on price, it shouldn't make a difference. That is unless the buyer has a desire for THAT particular suffix. For instance, I would be more than angry if I received a K-Date advertised as S/N 1543 and received S/N 1543a, even more so from a knowledgable Luger Collector.
As a buyer, I would probably ask if the matching statement meant grips and magazine, before I bought it. I don't know the knowledge level of the buyer, but it doesn't take three days to examine a Luger to determine the condition and confirmation of the matching statement (and serial number, if it's important).
As a buyer, I don't like surprises when I open the package. If you return the pistol, you pay freight both ways and in some cases the FFL dealer costs involved in the shipment both ways. This pretty well sucks, again IMO.
In this hypothetical case, I would try to give a novice a bit more slack, on the timing, than I would someone with much more experience. I believe that all or almost all dealers would tell the buyer not only no, but heck no.
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